Construction of Near-Capacity Protograph LDPC Code Sequences with Block-Error Thresholds

Density evolution for protograph Low-Density Parity-Check (LDPC) codes is considered, and it is shown that the message-error rate falls double-exponentially with iterations whenever the degree-2 subgraph of the protograph is cycle-free and noise level is below threshold. Conditions for stability of protograph density evolution are established and related to the structure of the protograph. Using large-girth graphs, sequences of protograph LDPC codes with block-error threshold equal to bit-error threshold and block-error rate falling near-exponentially with blocklength are constructed deterministically. Small-sized protographs are optimized to obtain thresholds near capacity for binary erasure and binary-input Gaussian channels.Comment: to appear in the IEEE Transactions on Communication

Deterministic Constructions for Large Girth Protograph LDPC Codes

The bit-error threshold of the standard ensemble of Low Density Parity Check (LDPC) codes is known to be close to capacity, if there is a non-zero fraction of degree-two bit nodes. However, the degree-two bit nodes preclude the possibility of a block-error threshold. Interestingly, LDPC codes constructed using protographs allow the possibility of having both degree-two bit nodes and a block-error threshold. In this paper, we analyze density evolution for protograph LDPC codes over the binary erasure channel and show that their bit-error probability decreases double exponentially with the number of iterations when the erasure probability is below the bit-error threshold and long chain of degree-two variable nodes are avoided in the protograph. We present deterministic constructions of such protograph LDPC codes with girth logarithmic in blocklength, resulting in an exponential fall in bit-error probability below the threshold. We provide optimized protographs, whose block-error thresholds are better than that of the standard ensemble with minimum bit-node degree three. These protograph LDPC codes are theoretically of great interest, and have applications, for instance, in coding with strong secrecy over wiretap channels.Comment: 5 pages, 2 figures; To appear in ISIT 2013; Minor changes in presentatio

Strong Secrecy on the Binary Erasure Wiretap Channel Using Large-Girth LDPC Codes

For an arbitrary degree distribution pair (DDP), we construct a sequence of low-density parity-check (LDPC) code ensembles with girth growing logarithmically in block-length using Ramanujan graphs. When the DDP has minimum left degree at least three, we show using density evolution analysis that the expected bit-error probability of these ensembles, when passed through a binary erasure channel with erasure probability $\epsilon$, decays as $\mathcal{O}(\exp(-c_1 n^{c_2}))$ with the block-length $n$ for positive constants $c_1$ and $c_2$, as long as $\epsilon$ is lesser than the erasure threshold $\epsilon_\mathrm{th}$ of the DDP. This guarantees that the coset coding scheme using the dual sequence provides strong secrecy over the binary erasure wiretap channel for erasure probabilities greater than $1 - \epsilon_\mathrm{th}$.Comment: 11 pages, 4 figures. Submitted to the IEEE Transactions on Information Forensics and Securit

Strong Secrecy for Erasure Wiretap Channels

We show that duals of certain low-density parity-check (LDPC) codes, when used in a standard coset coding scheme, provide strong secrecy over the binary erasure wiretap channel (BEWC). This result hinges on a stopping set analysis of ensembles of LDPC codes with block length $n$ and girth $\geq 2k$, for some $k \geq 2$. We show that if the minimum left degree of the ensemble is $l_\mathrm{min}$, the expected probability of block error is \calO(\frac{1}{n^{\lceil l_\mathrm{min} k /2 \rceil - k}}) when the erasure probability $\epsilon < \epsilon_\mathrm{ef}$, where $\epsilon_\mathrm{ef}$ depends on the degree distribution of the ensemble. As long as $l_\mathrm{min} > 2$ and $k > 2$, the dual of this LDPC code provides strong secrecy over a BEWC of erasure probability greater than $1 - \epsilon_\mathrm{ef}$.Comment: Submitted to the Information Theory Workship (ITW) 2010, Dubli

The Influence of Institutions on Coordination among the actors involved in Flood Management

Flooding is considered one of the most extreme and significant natural disasters that threaten the world’s cities. Especially, the urban flooding is threatening and a serious concern for both developed and developing countries. The impact of urban flooding has caused serious damage to properties, utilities, housing assets, interruptions in transportation, losses in industries, trade and whipping out employment. In November 2015, a sudden depression on the Bay of Bengal intensified into a cyclone and resulted in heavy and excessive rainfall in several parts of Tamil Nadu and instigated into the flood in Chennai. Although the main reason for the flooding was associated with excessive rainfall, the research undertaken by Arabindoo proved poor governance was the crucial element for flooding. The characteristics of flood management in Chennai are complex, highly fragmented with a large number of stakeholders. Thus, until there is a proper cooperation among the authorities, residents, city managers, and the public, it will be difficult to govern the worsening of flood problems. So, the research aims to understand the how the institutions assembled around flood management in Chennai influences coordination among the actors. In order to explain how aspects of coordination are influenced by the institutions in the context of Chennai flood management, the research has undergone a detailed theoretical analysis of institutions and coordination. From the theoretical analysis, essential concepts were drawn to conceptualize institutions and coordination. This research used the concepts of IAD principle to theoretically connect the concepts of Institutions and coordination. Through the theoretical concepts, the variables and indicators to analytically measure the institutions and coordination were developed. This research is a qualitative study carried out with a case study approach. Using the semi-structured interviews, the researcher gathered empirical data on the phenomenon of the study and the secondary data was utilized to triangulate the information collected through semi-structured interviews. The findings from the analysis show that the institutions in the flood management are characterized by a diversity of actors with varying strength, size, and power, the formal and the informal rules. On the other hand, the coordination among the actor is characterized by the communications that occur parallelly with few points of intersection, independent planning, executing and controlling and centralized commanding. Further, the institutional factors such as the social capital strength, jurisdictional division, shared responsibility, monitoring framework, the unclear roles and responsibility, distinct mandates, lack of sharing resources, weakness in the regulatory framework, lack of information, rigid bureaucratic hierarchy, and political prioritization positively or negatively influence the coordination among the actors. The main conclusion from the research shows that the institutional factors can obstruct and enable coordination among the actors. Especially, the research has highlighted the importance of the regulatory framework and the elements that are essential in the regulatory framework to structure coordination. It has also stressed the need for political actors to be accountable to the public and committed to enable coordination

Nanosafety

The nanomaterials resembling nanotubes, nanospheres, nanofertilizer, nanoherbicide, nanoinsecticide, and nanosheets have the physical, chemical, biological, mechanical, electrical and thermal properties. Still, the nanoparticles have very minute dimensions, enormous area and high reactivity they need the potential ability to penetrate in living cells quite rapidly. The petite size nanoparticles contain lofty surface area may cause higher reactivity with nearby particles. It is broadly predictable that there is a critical need for more information and facts about the implications of manufactured nanomaterials on personal fitness and surroundings. Concerns about potential risks to health that may arise during the making, management, use, and discarding of these nanomaterials have been spoken over the past few years. Consequently, strong research action is being undertaken in various institutions, and industries across the world to appraise their toxicity and spread of nanoparticle

Effect of Haemoglobin and Iron Status of the Antenatal Mothers on their Newborns at Birth: A Cross-sectional Study

Introduction: Iron deficiency (ID) anaemia in pregnant mothers can affect the iron reserves of their newborns and lead to anaemia later. The haematological indices and iron status of pregnant women and its correlation with their neonates is still unclear. Aim: To assess the correlation between maternal and cord blood Hb and iron status. Materials and Methods: The present cross-sectional study included 134 antenatal mothers, at term gestation without any significant antenatal complications. Complete haemogram, serum iron, ferritin, and iron binding capacity were assessed for these mothers before delivery and also from the cord blood samples of their newborns at birth. Statistical difference and correlation were observed using Chi-square test and Pearson’s correlation coefficient. Results: Maternal anaemia Hb <11 gm/dL) was observed in 62 (46.3%). The mean Hb and ferritin of the mothers were 11.06±1.02 gm/dL and 113.3±7.1 μg/L, respectively. The mean Hb and ferritin levels of the cord blood samples were 12.24±0.17 gm/dL and 214.3±20.1 μg/L, respectively. In univariate analysis, maternal Hb showed a significant correlation with cord blood Hb with Odds Ratio (OR) 0.508 and 95% Confidence Interval (CI): 0.428-0.603. The Pearson’s correlation showed a moderate correlation between mother and cord blood Packed Cell Volume (PCV) (r=0.344, p<0.001) and weak correlation between other maternal and cord blood iron indices and serum ferritin (r=0.191, p=0.027 and r=0.203, p=0.019). Conclusion: There is a significant correlation between maternal and cord blood Hb in term neonates. The study indicates that the haematological indices of pregnant women determine the neonatal Hb in term babies

Simulation of Rotary Motion Generated by Head-to-Head Carbon Nanotube Shuttles

International audienceA novel rotary nanomotor is described using two ax ially aligned, opposing chirality nanotube shuttles. Based on inter shell screw-likemotion of nanotubes, rotarymotion is generated by electrostatically pulling the two cores together. Simulations using molecular dynamics showthe generation of rotation fromarmchair nanotube pairs and their actuation properties. The simulation results point toward the use of these motors as building blocks in nanoelectromechanical systems and nanorobotic systems for sensing, actuation, and computation applications

Large duodenal GIST with massive liver secondaries melting under Imatinib: a case report

Gastrointestinal stromal tumors(GIST) have become a well established entity and its taxonomy is no more ambiguous. Better understanding of the cell of origin and immunohistochmical markers have made this possible. Their treatment has been revolutionized with the advent of targeted molecular therapy, namely Imatinib mesylate. Herein we report a rare and interesting case of a thirty year old South Indian Lady with an extremely large Duodenal GIST with massive Liver secondaries. The phenomenon of metastatic GIST responding to Imatinib mesylate is not new. What is interesting in this case is the enormous tumor load at the time of presentation as exemplified by the cross sectional images. This kind of tumor response and patient survival deserves documentatio